Fair isle question

I am making small wrist bands on dpns in a 1-1 rib with tubular cast on and bind off, and most of the color designs are straight forward enough – simple bands of color so i can just work in one yarn until i have the desired band width and then switch completely to the next color without ever having to float anything.
But a few of the designs i want to make have shapes in contrasting colors that need to be included in the center of the wristband, and i was thinking of using fair isle technique to create them.
My question is: is there a particular way to knit designs in contrasting colors onto a 1-1 rib that will look like what they are supposed to be even when the rib is stretched? Like, is there a way for me to knit a purple circle onto a yellow background and have it look like a circle when it is worn on somebody’s wrist?

edit: I should probably specify that i am not working from a pattern. I am completely winging it.

I’ve never done fair isle on ribbing so I’m not sure. I think it might not be what you’re expecting. Color looks different on purls. Have you tried it? What did you get?

It looked pretty bad. Purls are basically invisible. I’m thinking of maybe knitting the purls where I need to do the contrasting color. It’s probably gonna mess up the stretchiness of the rib in that part but maybe if I start with a couple extra stitches, I can keep the size the same.